From @cpansprout

perldebguts says​:

  o Each hash "%{"_<$filename"}" contains breakpoints and actions keyed
  by line number. Individual entries (as opposed to the whole hash)
  are settable.

This implies that breakpoints set on %{"_<..."} apply to the named file. That is not actually true, as every %{"_<..."} hash sets breakpoints on lines in @​DB​::dbline, regardless of which file it refers to. The assumption is that debuggers will alias *DB​::dbline to *{"_<..."} before setting any breakpoints.

Hence, all %{"_<..."} hashes are the same.

Is this a case where the documentation should be expanded to match the implementation? Or should we change the implementation to make each %{"_<..."} hash work on its corresponding @​{"_<..."} array? The latter seems more useful to me.

Demonstration​:

Run this with the -d switch and with PERL5DB set to 1​:

#!perl
sub DB​::DB { $DB​::single = 0, return if $DB​::single; print "ok\n"; exit }
${"_<".__FILE__}{5}=1; # set a breakpoint
sub foo {
  die; # line 5
}
foo();

$ PERL5DB=1 ./perl -Ilib -d foo
Died at foo line 5.

If I change the script to alias @​DB​::dbline to @​{"_<".__FILE__} first, it works​:

#!perl
sub DB​::DB { $DB​::single = 0, return if $DB​::single; print "ok\n"; exit }
*DB​::dbline = \@​{"_<".__FILE__}; ${"_<".__FILE__}{5}=1; # set a breakpoint
sub foo {
  die; # line 5
}
foo();

$ PERL5DB=1 ./perl -Ilib -d foo
ok

Flags​:
  category=core
  severity=low

Site configuration information for perl 5.19.4​:

Configured by sprout at Sun Sep 8 12​:35​:32 PDT 2013.

Summary of my perl5 (revision 5 version 19 subversion 4) configuration​:
  Local Commit​: 8bdbe21
  Ancestor​: 343e716
  Platform​:
  osname=darwin, osvers=12.2.0, archname=darwin-thread-multi-2level
  uname='darwin pint.local 12.2.0 darwin kernel version 12.2.0​: sat aug 25 00​:48​:52 pdt 2012; root​:xnu-2050.18.24~1release_x86_64 x86_64 '
  config_args='-de -Accflags=-DPERL_NO_COW -Dmad -Aoptimize=-O0 -DDEBUGGING -Duseithreads -Dusedevel -Dcc=g++ -Duse64bitint'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=define, usemultiplicity=define
  useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
  use64bitint=define, use64bitall=define, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='g++', ccflags ='-fno-common -DPERL_DARWIN -no-cpp-precomp -DPERL_NO_COW -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
  optimize='-O3 -O0 -g',
  cppflags='-no-cpp-precomp -fno-common -DPERL_DARWIN -no-cpp-precomp -DPERL_NO_COW -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
  ccversion='', gccversion='4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)', gccosandvers=''
  intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
  ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
  alignbytes=8, prototype=define
  Linker and Libraries​:
  ld='env MACOSX_DEPLOYMENT_TARGET=10.3 cc', ldflags =' -fstack-protector -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib
  libs=-ldbm -ldl -lm -lutil -lc
  perllibs=-ldl -lm -lutil -lc
  libc=, so=dylib, useshrplib=false, libperl=libperl.a
  gnulibc_version=''
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
  cccdlflags=' ', lddlflags=' -bundle -undefined dynamic_lookup -L/usr/local/lib -fstack-protector'

Locally applied patches​:
  1261f9a
  c2ee494
  21c314c
  7a7c28d
  0d72ebc
  8bdbe21

@​INC for perl 5.19.4​:
  lib
  /usr/local/lib/perl5/site_perl/5.19.4/darwin-thread-multi-2level
  /usr/local/lib/perl5/site_perl/5.19.4
  /usr/local/lib/perl5/5.19.4/darwin-thread-multi-2level
  /usr/local/lib/perl5/5.19.4
  /usr/local/lib/perl5/site_perl
  .

Environment for perl 5.19.4​:
  DYLD_LIBRARY_PATH (unset)
  HOME=/Users/sprout
  LANG=en_US.UTF-8
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)
  PATH=/usr/bin​:/bin​:/usr/sbin​:/sbin​:/usr/local/bin​:/usr/local/bin
  PERL_BADLANG (unset)
  SHELL=/bin/bash

From @rjbs

* Father Chrysostomos <perlbug-followup@​perl.org> [2013-09-15T15​:01​:58]

Hence, all %{"_<..."} hashes are the same.

Is this a case where the documentation should be expanded to match the
implementation? Or should we change the implementation to make each
%{"_<..."} hash work on its corresponding @​{"_<..."} array? The latter seems
more useful to me.

I agree​: the latter seems more useful.

--
rjbs

The RT System itself - Status changed from 'new' to 'open'

From @nwc10

On Mon, Sep 16, 2013 at 06​:25​:56PM -0400, Ricardo Signes wrote​:

* Father Chrysostomos <perlbug-followup@​perl.org> [2013-09-15T15​:01​:58]

Hence, all %{"_<..."} hashes are the same.

Is this a case where the documentation should be expanded to match the
implementation? Or should we change the implementation to make each
%{"_<..."} hash work on its corresponding @​{"_<..."} array? The latter seems
more useful to me.

I agree​: the latter seems more useful.

I really don't have much of an opinion of this.

The latter seems more useful. It seems somewhat wasteful that there is a
need to keep (re)aliasing *DB​::dbline just to set breakpoints on a different
file.

There are so few debuggers on CPAN that I suspect that there's almost no
debugger-like code elsewhere, so if there is any breakage, it will be
minimal and manageable.

Nicholas Clark

From @cpansprout

On Mon Sep 16 15​:26​:35 2013, perl.p5p@​rjbs.manxome.org wrote​:

* Father Chrysostomos <perlbug-followup@​perl.org> [2013-09-
15T15​:01​:58]

Hence, all %{"_<..."} hashes are the same.

Is this a case where the documentation should be expanded to match
the
implementation? Or should we change the implementation to make each
%{"_<..."} hash work on its corresponding @​{"_<..."} array? The
latter seems
more useful to me.

I agree​: the latter seems more useful.

I have changed it in commit 43e4250.

--

Father Chrysostomos

From [Unknown Contact. See original ticket]

On Mon Sep 16 15​:26​:35 2013, perl.p5p@​rjbs.manxome.org wrote​:

* Father Chrysostomos <perlbug-followup@​perl.org> [2013-09-
15T15​:01​:58]

Hence, all %{"_<..."} hashes are the same.

Is this a case where the documentation should be expanded to match
the
implementation? Or should we change the implementation to make each
%{"_<..."} hash work on its corresponding @​{"_<..."} array? The
latter seems
more useful to me.

I agree​: the latter seems more useful.

I have changed it in commit 43e4250.

--

Father Chrysostomos

@cpansprout - Status changed from 'open' to 'resolved'

From @KES777

Hi. After this commit it seems this section in DOC is meaningless. https://perldoc.perl.org/perldebguts.html#Debugger-Internal-Variables

Anybody can use %{ _< ... } directly